Several types of semiconductor devices include a doped semiconductor region that extends relatively deep into a semiconductor body and forms a vertical pn junction with an adjoining semiconductor region. A “vertical pn junction” is a pn junction that substantially extends in a vertical direction of the semiconductor body, which is a direction perpendicular to a main surface, such as a front surface or a rear surface, of the semiconductor body. For example, a superjunction transistor includes compensation regions that extend deep into a drift region and form vertical pn junctions with the drift region. In a JFET (Junction Field-Effect Transistor), a source region can be implemented to extend deep into a semiconductor body and form a pn junction with a body region.
Compensation regions of a superjunction device can be produced using a multiple epitaxy process. In this process, a layer stack is formed by producing several epitaxially grown layers above one another, and introducing dopant atoms into each layer in a masked implantation process. An annealing process after the end of the multiple epitaxy process causes the implanted dopant atoms to diffuse in the layer stack with and to be activated, thereby forming the compensation regions. A multiple epitaxy process, however, is expensive
A source region of a JFET can be formed by etching a trench into a channel region (i.e. a body region) of the JFET and by implanting dopant atoms either into sidewalls of the trench or into a mask layer from where they are scattered into the sidewalls. However, this sequence requires forming a deep source region requires a wide trench for, and may not be very efficient.
There is therefore a need to provide an efficient and economic method for producing a doped region, in particular a doped region that extends deep into a semiconductor body.